Ink jet printing method

ABSTRACT

An ink jet printing method, comprising the steps of:  
     A) providing an ink jet printer that is responsive to digital data signals;  
     B) loading the printer with an ink jet recording element comprising a support having thereon an image-receiving layer;  
     C) loading the printer with an ink jet ink composition comprising water, a humectant, a polyvalent transition metal complex of an 8-heterocyclylazo -5-hydroxy-quinoline and an anti-kogation material comprising an alkali metal salt of a monobasic organic or inorganic acid; and  
     D) printing on the image-receiving layer using the ink jet ink composition in response to the digital data signals.  
     Examples of anti-kogation materials useful in the invention include sodium hexanoate, sodium sulfate, sodium propionate, sodium benzoate, sodium p-toluenesulfonate, sodium acetate, sodium bromide, sodium nitrate, potassium nitrate, lithium nitrate, lithium acetate, tetramethylammonium acetate and tetrabutylammonium bromide.

CROSS REFERENCE TO RELATED APPLICATION

[0001] Reference is made to commonly assigned, co-pending U.S. patentapplication Ser. No.______ by Erdtmann et al., (Docket 82240) filed ofeven date herewith entitled “Ink Jet Ink Composition”.

FIELD OF THE INVENTION

[0002] This invention relates to an ink jet printing method using acertain metal complex useful as a colorant in combination with ananti-kogation material in an ink jet ink composition.

BACKGROUND OF THE INVENTION

[0003] Ink jet printing is a non-impact method for producing images bythe deposition of ink droplets in a pixel-by-pixel manner to animage-recording element in response to digital signals. There arevarious methods which may be utilized to control the deposition of inkdroplets on the image-recording element to yield the desired image. Inone process, known as continuous ink jet, a continuous stream ofdroplets is charged and deflected in an imagewise manner onto thesurface of the image-recording element, while unimaged droplets arecaught and returned to an ink sump. In another process, known asdrop-on-demand inkjet, individual ink droplets are projected as neededonto the image-recording element to form the desired image. Commonmethods of controlling the projection of ink droplets in drop-on-demandprinting include piezoelectric transducers and thermal bubble formation.Ink jet printers have found broad applications across markets rangingfrom industrial labeling to short run printing to desktop document andpictorial imaging.

[0004] The inks used in the various ink jet printers can be classifiedas either dye-based or pigment-based. A dye is a colorant, which isdissolved in the carrier medium. A pigment is a colorant that isinsoluble in the carrier medium, but is dispersed or suspended in theform of small particles, often stabilized against flocculation andsettling by the use of dispersing agents. The carrier medium can be aliquid or a solid at room temperature in both cases. Commonly usedcarrier media include water, mixtures of water and organic co-solventsand high boiling organic solvents, such as hydrocarbons, esters,ketones, etc.

[0005] The choice of a colorant in ink jet systems is critical to imagequality. For colors such as cyan, magenta, yellow, green, orange, etc.,the peak wavelength (λ-max), the width of the absorption curve and theabsence of secondary absorptions are important. The colorants shouldalso have a high degree of light fastness after printing onto theink-receiving element. For aqueous dye-based inks, the dyes need to besufficiently soluble in water to prepare a solution that is capable ofproducing adequate density on the receiving element and stable forextended periods of storage without precipitation. High quality ink jetprinting with dye-based inks requires dyes which will provide bothbright hue and good light stability. It is difficult to find dyes whichmeet all of these requirements, particularly magenta dyes.

[0006] Kogation occurs on a thermal ink jet heater plate as a result ofthermal decomposition of ink components or accumulation of intact inkcomponents. An anti-kogation material can be used in an ink jet inkcomposition to prevent buildup of thermal decomposition products on aheater plate in a thermal ink jet print head.

[0007] U.S. Pat. No. 6,001,161 relates to a magenta metal complex dyefor an inkjet ink. However, there is a problem with this dye in that themaximum density of a printed image decreases over time with magenta inkscontaining this dye.

[0008] U.S. Pat. No. 6,059,868 relates to anti-kogation materials usefulin inkjet printing. However, when these anti-kogation materials are usedwith metal-complex dyes, the resulting printed image have poor imagequality.

[0009] It is an object of this invention to provide an ink jet printingmethod using an ink jet ink composition containing a magenta metalcomplex in combination with an anti-kogation material that has both goodlight stability and bright hue, and is able to provide consistentdensity when printed in a thermal ink jet printer.

SUMMARY OF THE INVENTION

[0010] This and other objects are achieved in accordance with thisinvention which relates to an inkjet printing method, comprising thesteps of:

[0011] A) providing an ink jet printer that is responsive to digitaldata signals;

[0012] B) loading the printer with an ink jet recording elementcomprising a support having thereon an image-receiving layer,

[0013] C) loading the printer with an ink jet ink composition comprisingwater, a humectant, a polyvalent transition metal complex of an8-heterocyclylazo -5-hydroxy-quinoline and an anti-kogation materialcomprising an alkali metal salt of a monobasic organic or inorganicacid; and

[0014] D) printing on the image-receiving layer using the ink jet inkcomposition in response to the digital data signals.

[0015] Use of this ink composition in the inkjet printing method of theinvention provides images with a combination of outstanding lightstability, bright magenta hue and consistent densities.

DETAILED DESCRIPTION OF THE INVENTION

[0016] In a preferred embodiment of the invention, the polyvalenttransition metal complexes of an 8-heterocyclylazo-5-hydroxyquinolineemployed have the following general structure:

[0017] wherein:

[0018] M represents a polyvalent transition metal ion;

[0019] each L independently represents a neutral or anionic ligand;

[0020] each X, Y and Z independently represents a substituted orunsubstituted alkyl group of 1-6 carbon atoms, a substituted orunsubstituted alkyl group of 6-10 carbon atoms, a substituted orunsubstituted hetaryl group of 5-10 atoms, halogen, cyano, nitro, asubstituted or unsubstituted alkoxycarbonyl group of 1-6 carbon atoms, asubstituted or unsubstituted alkoxy group of 1-6 carbon atoms, hydroxy,a polyoxyalkylene group of 2-20 alkylene oxide residues, carboxy or asalt thereof, sulfo or a salt thereof, phospho or a salt thereof,carbamoyl, a substituted or unsubstituted alkyl-, aralkyl-, aryl-,diaryl- or dialkyl-carbamoyl group of 1-20 carbon atoms, sulfamoyl, asubstituted or un substituted alkyl-, aralkyl-, aryl-, diaryl- ordialkyl-sulfamoyl group of 1-20 carbon atoms, acylamino, sulfonylamino,amino, a substituted or unsubstituted alkyl-, aralkyl-, aryl-, diaryl-or dialkyl-amino group of 1-20 carbon atoms or a quaternary ammonium orphosphonium group;

[0021] Q represents the atoms necessary to complete a 5- or 6-memberedheterocyclic ring;

[0022] n represents 2 or 3;

[0023] m represents an integer from 1-3;

[0024] each p and r independently represents an integer from 0-3;

[0025] q represents 0, 1 or 2;

[0026] two or more of L may be joined together to form a bi- ortridentate ligand which may optionally comprise another polydentatemolecule of the same or different structure as shown above;

[0027] one or more of L may be combined with X and/or Z;

[0028] one or more of X, Y and Z, together with the carbon to which theyare attached, may independently represent a ring nitrogen; and

[0029] any two of X, Y or Z may be joined together to form a 5-7membered saturated or unsaturated ring;

[0030] Compositions in which two or more of the above metal complex dyesrepresented by structure 1 are joined covalently are also considered tobe within the scope of this invention.

[0031] Preferred transition metal ions for 1 include Ni²⁺, Cu²⁺, Zn²⁺,Fe²⁺, Fe³⁺, Cr³⁺, Pd²⁺, Pt²⁺and Co²⁺.

[0032] Examples of neutral ligands (L) for 1 include water, pyridine,morpholine and ammonia. Examples of bi- and tri-dentate ligands includebipyridine, terpyridine, iminodiacetate, glycine and 8-hydroxyquinoline.

[0033] Examples of anionic ligands (L) include acetate, chloride andcyanate.

[0034] For X, Y and Z in 1, examples of a substituted or unsubstitutedalkyl group include methyl, ethyl, isopropyl, hydroxyethyl,3-(N,N-dimethylamino) propyl, sulfatoethyl and benzyl. Examples of asubstituted or unsubstituted aryl group include phenyl, naphthyl,4-chlorophenyl and 2-carboxyphenyl. Examples of a substituted orunsubstituted hetaryl group include pyridyl, imidazolyl and quinolyl.Examples of halogen include chloro, fluoro, bromo and iodo. Examples ofa substituted or unsubstituted alkoxy group include methoxy, isopropoxy,2-hydroxyethoxy and carboxymethoxy. Useful salts of carboxy, sulfo,phospho and sulfato include sodium, lithium, potassium,triethanolammonium, pyridinium and tetramethylammonium. Examples of asubstituted or unsubstituted alkyl-, aralkyl-, aryl-, diaryl- ordialkyl-carbamoyl group include N-methylcarbamoyl,N-methyl-N-(3-sulfophenyl)-carbamoyl, N-p-(trimethylammonium)phenylcarbamoyl and N,N-bis (4-carboxyphenyl) carbamoyl. Examples of asubstituted or unsubstituted alkyl-, aralkyl-, aryl-, diaryl- ordialkyl-sulfamoyl group include N-methylsulfamoyl, N-methyl-N-(3-sulfophenyl)-sulfamoyl, N-p-(trimethylammonium)phenylsulfamoyl andN,N-bis (4-carboxyphenyl)sulfamoyl. Examples of an acylamino groupinclude acetamido, carboxyethylacetamido and benzamido. Examples of aureido group include n-methylureido, ureido and 3,5-biscarboxyphenylureido. Examples of a sulfonylamino group includemethanesulfonamido, p-toluenesulfonamido and2-(trimethlyammonium)ethanesulfonamido. Examples of a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-amino groupinclude methylamino, N,N-dimethylamino, carboxymethylamino and2,5-disulfoanilino. disulfoanilino. Examples of a quaternary ammoniumgroup include trimethylammonium and benzyldimethylammonium. Examples ofa phosphonium group include triphenylphosphonium andtrimethylphosphonium.

[0035] Examples of heterocyclic ring systems completed by the atomsrepresented by Q include pyridine, pyrazine, quinoline, thiazole,benzothiazole and pyrazole.

[0036] In a preferred embodiment of the invention, M is Ni²⁺. In anotherpreferred embodiment, L_(m) comprises an8-heterocyclylazo-5-hydroxyquinoline. In yet another preferredembodiment, X is a chloro, methyl, alkoxy or carboxy. In still anotherpreferred embodiment, Y is hydrogen, and Z is hydrogen oralkylsulfamoyl. In still yet another preferred embodiment, Q representsthe atoms necessary to complete a pyridine ring.

[0037] U.S. Pat. No. 4,420,550 and Example 1 hereafter describe generalsynthetic procedures for preparing the metal complexes employed in thisinvention.

[0038] Representative examples of dyes which may be employed in thisinvention include the following:

Dye M X₁ X₂ Z λ-max¹ 1 Ni Cl CO₂H SO₂NH(i-Pr) 559 2 Cu Cl CO₂HSO₂NH(i-Pr) 547 3 Ni Cl CO₂Na H 550 4 Ni Cl CO₂H H 551 5 Ni H CO₂H H 5466 Ni CH₃ CO₂H H 552 7 Ni CO₂H CO₂H H 554

[0039]

Dye M^(n+) X Y Z  8 Ni²⁺ 3-CO₂H H H 4-Cl  9 Co²⁺ 2-Cl 6-CH₃ 5′-SO₃-Na⁺3-CH₃ 10 Cr³⁺ 2-Cl H 6′-Cl 3-CONH-(C₂H₄N(CH₃)₂) 11 Ni²⁺ H H4′,5′-(CO₂H)₂ 12 Cu²⁺ 2-NHC₃H₆N-(CH₃)₂ 6,7-(CH₃)₂ H 13 Ni²⁺ 2-Cl 7-CO₂H5′-Cl 3-[C₆H₃-3,5-(SO₃Na)₂] 14 Ni²⁺ 2,3-Cl₂ 6-OH 5′-SO₂NH[C₃H₆N(CH₃)₂]₂15 Cu²⁺ 3-CONHC₂H₄-(N⁺CH₃)₃Cl⁻ 6-CN 4′-CONH₂ 16 Ni²⁺ 2-Cl H H3-SO₂NHC₂H₄OSO₃-Na⁺

[0040]

[0041] As noted above, an anti-kogation material is used in the ink jetcomposition employed in the invention and comprises an alkali metal saltof a monobasic organic or inorganic acid. In another preferredembodiment of the invention, the anti-kogation material is sodiumhexanoate, sodium sulfate, sodium propionate, sodium benzoate, sodiump-toluenesulfonate, sodium acetate, sodium bromide, sodium nitrate,potassium nitrate, lithium nitrate, lithium acetate, tetramethylammoniumacetate or tetrabutylammonium bromide.

[0042] A humectant is employed in the ink jet composition employed inthe invention to help prevent the ink from drying out or crusting in theorifices of the printhead. Examples of humectants which can be usedinclude polyhydric alcohols, such as ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, tetraethylene glycol, polyethyleneglycol, glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol andthioglycol, lower alkyl mono- or di-ethers derived from alkyleneglycols, such as ethylene glycol mono-methyl or mono-ethyl ether,diethylene glycol mono-methyl or mono-ethyl ether, propylene glycolmono-methyl or mono-ethyl ether, triethylene glycol mono-methyl ormono-ethyl ether, diethylene glycol di-methyl or di-ethyl ether, anddiethylene glycol monobutylether; nitrogen-containing cyclic compounds,such as 2-pyrrolidone, N-methyl -2-pyrrolidone, and1,3-dimethyl-2-imidazolidinone; and sulfur-containing compounds such asdimethyl sulfoxide and tetramethylene sulfone. A preferred humectant forthe composition of the invention is diethylene glycol, glycerol,2-pyrrolidone or diethylene glycol monobutylether.

[0043] Water-miscible organic solvents may also be added to the aqueousink employed in the invention to help the ink penetrate the receivingsubstrate, especially when the substrate is a highly sized paper.Examples of such solvents include alcohols, such as methyl alcohol,ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol,and tetrahydrofurfuryl alcohol; ketones or ketoalcohols such as acetone,methyl ethyl ketone and diacetone alcohol; ethers, such astetrahydrofuran and dioxane; and esters, such as, ethyl lactate,ethylene carbonate and propylene carbonate.

[0044] Surfactants may be added to adjust the surface tension of the inkto an appropriate level. The surfactants may be anionic, cationic,amphoteric or nonionic.

[0045] A biocide may be added to the composition employed in theinvention to suppress the growth of micro-organisms such as molds,fungi, etc. in aqueous inks. A preferred biocide for the ink compositionemployed in the present invention is Proxel® GXL (Zeneca SpecialtiesCo.) at a final concentration of 0.05-0.5 wt. %.

[0046] The pH of the aqueous ink compositions employed in the inventionmay be adjusted by the addition of organic or inorganic acids or bases.Useful inks may have a preferred pH of from about 2 to 10, dependingupon the type of dye or pigment being used. Typical inorganic acidsinclude hydrochloric, phosphoric and sulfuric acids. Typical organicacids include methanesulfonic, acetic and lactic acids. Typicalinorganic bases include alkali metal hydroxides and carbonates. Typicalorganic bases include ammonia, triethanolamine andtetramethylethlenediamine.

[0047] A typical ink composition employed in the invention may comprise,for example, the following substituents by weight: colorant (0.05-20%),water (20-95%), humectant (5-70%), water miscible co-solvents (2-20%),surfactant (0.1-10%), biocide (0.05-5%) and pH control agents (0.1-10%).

[0048] Additional additives which may optionally be present in the inkjet ink composition employed in the invention include thickeners,conductivity enhancing agents, drying agents, and defoamers.

[0049] The ink jet inks employed in this invention may be employed inink jet printing wherein liquid ink drops are applied in a controlledfashion to an ink receptive layer substrate, by ejecting ink dropletsfrom a plurality of nozzles or orifices of the print head of an inkjetprinter.

[0050] Ink-receptive substrates useful in inkjet printing are well knownto those skilled in the art. Representative examples of such substratesare disclosed in U.S. Pat. Nos. 5,605,750; 5,723,211; and 5,789,070 andEP 813 978 Al, the disclosures of which are hereby incorporated byreference.

[0051] The following examples illustrate the utility of the presentinvention.

EXAMPLES Example 1 Synthesis of Dye 6

[0052] A solution of 2.75 g (0.01 mole)ethyl-(2-methyl-5,8-dimethoxy)-quinoline -3-carboxylate (see U.S. Pat.No. 4,656,283) in 50 mL of tetrahydrofuran (THF) was diluted with 100 mLof ethylacetate. To this solution was added a solution of 13.71 g (0.025mole) of ceric ammonium nitrate in 50 mL of water and the 2-phasemixture stirred at room temperature for 1.5 hr. The phases wereseparated and the upper, organic layer washed twice with 25 mL of waterand once with saturated NaCl. After drying over MgSO₄, the organic layerwas evaporated to dryness at less than 40° C. The residual solid wassuspended in 100 mL of ethanol containing 0.5 mL of concentratedhydrochloric acid and treated with a solution of 1.09 g (0.01 mole) of2-hydrazinopyridine in 20 mL of ethanol containing 0.5 mL ofconcentrated hydrochloric acid. After stirring 18 hr at ambienttemperature and chilling to 0° C., the solid product was collected byfiltration. The crude dye-ester was purified by digestion with 25 mL ofboiling ethanol, chilling and filtering. The yield was 1.3 g (51% oftheory) of ethyl-(2-methyl-5-hydroxy-8-[2-pyridylazo])-quinoline-3-carboxylate as a dark redsolid.

[0053] The dye-ester from above (1.18 g, 0.0035 mole) was hydrolyzed bywarming at 40° C. in a mixture of THF/methanol/water (7:25:5) containing0.7 g NaOH (0.0175 mole) for 2 hr. After dilution with 100 mL water, thedeep orange solution was acidified to pH˜3 with dilute hydrochloric acidand the resulting yellow-orange solid collected by filtration. The crudedye-acid was purified by digestion with 15 mL of boiling acetonitrile,chilling and filtering to give 1.0 g (92% of theory) of2-methyl-5-hydroxy-8-(2-pyridylazo)-quinoline-3-carboxylic acid.

[0054] The dye-acid from above (1.0 g, 0.00325 mole) was suspended in 10mL of dimethylformamide and treated with a solution of 0.4 g (0.00162mole) nickel(II)acetate tetrahydrate in 3 mL water. The red-magentasolution was warmed at 75° C. for 1 hour, cooled to ambient temperatureand diluted with 50 mL water and the crude Dye 6 was collected byfiltration. After digestion with 20 mL of acetonitrile, chilling andfiltering, 1.0 g (91% of theory) of Dye 6 was obtained as a darkred-green solid. The UV-visible spectrum was obtained in 1%triethanolamine/water and gave a λ-max of 552 nm. The mass spectrum wasdetermined with a quadropole mass spectrometer utilizing ElectrosprayIonization set up to detect negatively charged ions. The spectrumexhibited major peaks at m/e 671 and 673 consistent with the structureof Dye 6 (formula weight 672, ⁵⁸Ni),

[0055] Preparation of inks

[0056] Control Ink C-1:

[0057] One liter of ink was prepared containing 0.55% dry Dye 6, 7.5%diethylene glycol, 7.5% glycerol, 4.0% 2-pyrrolidinone, 0.30% Surfynol®465 (Air Products), 0.10% of Rhodia Rhodasurf® LA-9, and the balancedeionized water. The ink pH was adjusted to approximately 7 by theaddition of triethanolamine. The ink loaded into a 25.4 cm AlleghenyBradford filter housing and filtered through a Pall® 4.5μ filterfollowed by a Pall® DFA filter.

[0058] Control Ink C-2:

[0059] One liter of ink was prepared like Control Ink C-1, except 0.90%ammonium nitrate (Acros) was added. Ammonium nitrate is an anti-kogationmaterial described in U.S. Pat. No. 6,059,868 (see Liquids 1b, 1c, 2b,2c, 3b and 3c in Table VI).

[0060] Control Ink C-3:

[0061] One liter of ink was prepared like Control Ink C-1, except 0.60%sodium carbonate (Aldrich), an alkali metal salt of a dibasic inorganicacid, was added.

[0062] Control Ink C-4:

[0063] One liter of ink was prepared like Control Ink C-1, except 1.26%sodium tartrate dihydrate (Kodak), an alkali metal salt of a dibasicorganic acid, was added.

[0064] Control Ink C-5:

[0065] One liter of ink was prepared like Control Ink C-1, except 1.08%sodium citrate dihydrate (Kodak), an alkali metal salt of a dibasicorganic acid, was added.

[0066] Invention Ink 1:

[0067] One liter of ink was prepared like Control Ink C-1, except 0.90%sodium hexanoate (Aldrich) was added.

[0068] Invention Ink 2:

[0069] One liter of ink was prepared like Control Ink C-1, except 1.56%sodium sulfate (Aldrich) was added.

[0070] Invention Ink 3:

[0071] One liter of ink was prepared like Control Ink C-1, except 1.07%sodium propionate (Aldrich) was added.

[0072] Invention Ink 4:

[0073] One liter of ink was prepared like Control Ink C-1, except 1.60%sodium benzoate (Kodak) was added.

[0074] Invention Ink 5:

[0075] One liter of ink was prepared like Control Ink C-1, except 2.16%sodium p-toluene sulfonate, sodium salt (Aldrich) was added.

[0076] Invention Ink 6:

[0077] One liter of ink was prepared like Control Ink C-1, except 1.13%potassium nitrate (Aldrich) was added.

[0078] Invention Ink 7:

[0079] One liter of ink was prepared like Control Ink C-1, except 0.76%lithium nitrate (Aldrich) was added.

[0080] Invention Ink 8:

[0081] One liter of ink was prepared like Control Ink C-1, except 0.90%sodium nitrate (Kodak) was added.

[0082] Invention Ink 9:

[0083] One liter of ink was prepared like Control Ink C-1, except 0.90%sodium acetate (Aldrich) was added.

[0084] Invention Ink 10:

[0085] One liter of ink was prepared like Control Ink C-1, except 3.53%tetrabutylammonium bromide (Aldrich) was added.

[0086] Invention Ink 11:

[0087] One liter of ink was prepared like Control Ink C-1, except 1.11%sodium bromide (EM Science) was added.

[0088] Printing of test images

[0089] Each of the above inks was filled into a reservoir of an Encad700 printer and into an empty Encad GS ink cartridge. An image qualitytarget that contained a small 2.0 square cm magenta patch was printedonto KODAK PROFESSIONAL EI Premium Media and the initial density wasmeasured using an X-Rite densitometer. A prime target was printed tomake sure all of the nozzles were firing correctly and there were noelectrical failures. An electrical failure may occur when there iseither an electrical short to ground so that the heater is by-passed andinsufficient heat is generated in the heater, or there is a significantincrease in resistance in the heater circuit, which would also inhibitgeneration in the heater in the printhead. Either of these phenomenacauses the nozzle not to operate.

[0090] A large 100% magenta patch target (92 by 610 cm) was then printedthat consumed 25 ml of ink. A second image quality target was printedonto KODAK PROFESSIONAL El Premium Media and the density wasre-measured. A prime target was printed to make sure all of the nozzleswere firing correctly and there were no electrical failures. This testwas repeated until a total of 300 ml of ink was fired through a singleEncad printhead. The percent density retained between the initial imagequality target and the image quality target printed after 300ml of inkhad been fired is shown in Table 1. If any nozzles have had anelectrical failure during the 300ml test, it is recorded in Table 1, andthe ink is considered unacceptable.

[0091] Each image quality target was evaluated for image defects such asbanding, bronzing, or bleed. A qualitative rating of excellent, good,fair, and poor was given to each ink printed onto KODAK PROFESSIONAL EIPremium Media, and is shown in Table 1. An ink must have improveddensity retention, excellent or good image quality, and no electricalfailures to be considered acceptable. TABLE 1 Percent Density InkRetained Image Quality Electrical Failure 1 83% Excellent No 2 83%Excellent No 3 89% Excellent No 4 89% Excellent No 5 85% Excellent No 610% Excellent No 7 95% Excellent No 8 89% Excellent No 9 88% ExcellentNo 10  93% Good No 11  86% Excellent No C-1 66% Excellent No C-2 100% Poor No C-3 100%  Excellent Yes C-4 79% Excellent Yes C-5 84% ExcellentYes

[0092] The above results show that the inkjet ink compositions employedin the invention yield images with excellent image quality, haveimproved retained density, and do not cause electrical failures of theprinthead.

[0093] The invention has been described in detail with particularreference to certain preferred embodiments thereof, but it will beunderstood that variations and modifications can be effected within thespirit and scope of the invention.

What is claimed is:
 1. An ink jet printing method, comprising the stepsof: A) providing an ink jet printer that is responsive to digital datasignals; B) loading said printer with an ink jet recording elementcomprising a support having thereon an image-receiving layer; C) loadingsaid printer with an ink jet ink composition comprising water, ahumectant, a polyvalent transition metal complex of an 8-heterocyclylazo-5-hydroxy-quinoline and an anti-kogation material comprising an alkalimetal salt of a monobasic organic or inorganic acid; and D) printing onsaid image-receiving layer using said ink jet ink composition inresponse to said digital data signals.
 2. The method of claim 1 whereinsaid complex has the following structure:

wherein: M represents a polyvalent transition metal ion; each Lindependently represents a neutral or anionic ligand; each X, Y and Zindependently represents a substituted or unsubstituted alkyl group of1-6 carbon atoms, a substituted or unsubstituted aryl group of 6-10carbon atoms, a substituted or unsubstituted hetaryl group of 5-10atoms, halogen, cyano, nitro, a substituted or unsubstitutedalkoxycarbonyl group of 1-6 carbon atoms, a substituted or unsubstitutedalkoxy group of 1-6 carbon atoms, hydroxy, a polyoxyalkylene group of2-20 alkylene oxide residues, carboxy or a salt thereof, sulfo or a saltthereof, phospho or a salt thereof, carbamoyl, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-carbamoylgroup of 1-20 carbon atoms, sulfamoyl, a substituted or unsubstitutedalkyl-, aralkyl-, aryl-, diaryl- or dialkyl-sulfamoyl group of 1-20carbon atoms, acylamino, sulfonylamino, amino, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-amino group of1-20 carbon atoms or a quaternary ammonium or phosphonium group; Qrepresents the atoms necessary to complete a 5- or 6-memberedheterocyclic ring; n represents 2 or 3; m represents an integer from1-3; each p and r independently represents an integer from 0-3; qrepresents 0, 1 or 2; two or more of L may be joined together to form abi- or tridentate ligand which may optionally comprise anotherpolydentate molecule of the same or different structure as shown above;one or more of L may be combined with X and/or Z; one or more of X, Yand Z, together with the carbon to which they are attached, mayindependently represent a ring nitrogen; and any two of X, Y or Z may bejoined together to form a 5-7 membered saturated or unsaturated ring; 3.The method of claim 2 wherein M is Ni²⁺.
 4. The method of claim 2wherein L_(m) comprises an 8-heterocyclylazo -5-hydroxyquinoline.
 5. Themethod of claim 2 wherein X is chloro, methyl, alkoxy or carboxy.
 6. Themethod of claim 2 wherein Y is hydrogen.
 7. The method of claim 2wherein Z is hydrogen or alkylsulfamoyl.
 8. The method of claim 2wherein Q represents the atoms necessary to complete a pyridine ring. 9.The method of claim 1 wherein said composition also contains awater-miscible organic solvent.
 10. The method of claim 1 wherein saidhumectant is diethylene glycol, glycerol, 2-pyrrolidinone or diethyleneglycol monobutylether.
 11. The method of claim 1 wherein said metalcomplex comprises about 0.05 to about 5% by weight of said inkjet inkcomposition.
 12. The method of claim 1 wherein said anti-kogationmaterial is present in said ink jet ink composition in an amount of fromabout 0.1 to about 10 weight %.
 13. The method of claim 1 wherein saidanti-kogation material is present in said ink jet ink composition in anamount of from about 0.25 to about 5 weight %.
 14. An ink jet printingmethod, comprising the steps of: A) providing an inkjet printer that isresponsive to digital data signals; B) loading said printer with an inkjet recording element comprising a support having thereon animage-receiving layer; C) loading said printer with an ink jet inkcomposition comprising water, a humectant, a polyvalent transition metalcomplex of an 8-heterocyclylazo -5-hydroxy-quinoline and ananti-kogation material comprising sodium hexanoate, sodium sulfate,sodium propionate, sodium benzoate, sodium p-toluenesulfonate, sodiumacetate, sodium bromide, sodium nitrate, potassium nitrate, lithiumnitrate, lithium acetate, tetramethylammonium acetate ortetrabutylammonium bromide; and D) printing on said image-receivinglayer using said ink jet ink composition in response to said digitaldata signals.
 15. The method of claim 14 wherein said complex has thefollowing structure:

wherein: M represents a polyvalent transition metal ion; each Lindependently represents a neutral or anionic ligand; each X, Y and Zindependently represents a substituted or unsubstituted alkyl group of1-6 carbon atoms, a substituted or unsubstituted aryl group of 6-10carbon atoms, a substituted or unsubstituted hetaryl group of 5-10atoms, halogen, cyano, nitro, a substituted or unsubstitutedalkoxycarbonyl group of 1-6 carbon atoms, a substituted or unsubstitutedalkoxy group of 1-6 carbon atoms, hydroxy, a polyoxyalkylene group of2-20 alkylene oxide residues, carboxy or a salt thereof, sulfo or a saltthereof, phospho or a salt thereof, carbamoyl, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-carbamoylgroup of 1-20 carbon atoms, sulfamoyl, a substituted or unsubstitutedalkyl-, aralkyl-, aryl-, diaryl- or dialkyl-sulfamoyl group of 1-20carbon atoms, acylamino, sulfonylamino, amino, a substituted orunsubstituted alkyl-, aralkyl-, aryl-, diaryl- or dialkyl-amino group of1-20 carbon atoms or a quaternary ammonium or phosphonium group; Qrepresents the atoms necessary to complete a 5- or 6-memberedheterocyclic ring; n represents 2 or 3; m represents an integer from1-3; each p and r independently represents an integer from 0-3; qrepresents 0, 1 or 2; two or more of L may be joined together to form abi- or tridentate ligand which may optionally comprise anotherpolydentate molecule of the same or different structure as shown above;one or more of L may be combined with X and/or Z; one or more of X, Yand Z, together with the carbon to which they are attached, mayindependently represent a ring nitrogen; and any two of X, Y or Z may bejoined together to form a 5-7 membered saturated or unsaturated ring;16. The method of claim 14 wherein said metal complex comprises about0.05 to about 5% by weight of said ink jet ink composition.
 17. Themethod of claim 14 wherein said anti-kogation material is present insaid ink jet ink composition in an amount of from about 0.1 to about 10weight %.
 18. The method of claim 14 wherein said anti-kogation materialis present in said ink jet ink composition in an amount of from about0.25 to about 5 weight %.